The descent of an aircraft from a cruise phase to a landing phase may be controlled for a variety of reasons, which may have contradictory goals. When fuel conservation is the primary goal, it is common to perform an idle descent, where the engine is set at idle, i.e. minimum thrust, and controlling the path of descent using control surfaces. During an idle descent, the aircraft may encounter an over-speed condition, which is currently solved by the pilot deploying speed brakes, generating a great amount of noise, which many passengers do not like. For aircraft without speed brakes, other solutions, typically much less desirable, may be used.
Alternatively, the pilot can apply a pitch input into the aircraft, which change the trajectory and consumes additional fuel and defeating the purpose of the idle descent. Another alternative solution is to utilize one or more of the aircraft avionics, like the Flight Management System and/or Flight Guidance System (FMS & FGS), and leave the engine throttle above idle, at approximately 10% and decrease the throttle when an over-speed condition occurs, which also consumes additional fuel and defeats the purpose of an idle descent.